Printed circuit board with compound via

A printed circuit board with compound via, the printed circuit board comprising:

• a substrate including:
• a first signal layer, wherein the first signal layer is the top layer of the substrate;
• a first and a second reference layer, wherein the first reference layer with a first reserved opening formed thereon is adjacent to the first signal layer, the second reference layer is not adjacent to the first signal layer, wherein the first reserved opening includes a first rectangular opening, a second rectangular opening, and a first communicating opening communicating the first rectangular opening with the second rectangular opening, the normal projection of the first rectangular opening on the signal layer overlaps a minimal rectangular area capable of enclosing the first pad set, the normal projection of the second rectangular opening on the signal layer overlaps a minimal rectangular area capable of enclosing the second pad set;
• and
• a first to a third pair of pads mounted on the first signal layer for soldering electronic components, wherein the first pair of pads includes a first pad and a second pad, the second pair of pads includes a third pad and a fourth pad, the third pair of pads includes a fifth pad and a sixth pad, the first pad, the third pad, and the fifth pad jointly form a first pad set, the second pad, the fourth pad, and the sixth pad jointly form a second pad set;
• and
• a pair of through holes passing through the substrate, wherein each of the through holes passes through the second pair of pads such that the through hole and the second pair of pads jointly form a pair of compound vias, the normal projection of the first communicating opening on the first signal layer overlaps a portion of a minimal rectangular area capable of enclosing the pair of compound vias between the minimal rectangular area capable of enclosing the first pad set and the minimal rectangular area capable of enclosing the second pad set.